To improve efficiency, methods are being sought for adapting heat engines, such as for example automobile engines, gas turbines and the like, to run at temperatures higher than now used. Ceramics are believed to be particularly suitable as materials for bearing surfaces within very high-temperature engines. However, a hindrance to high temperature engine operations, for example operations in excess of about 475.degree. C., has involved lubrication of load bearing surfaces.
At lower engine operating temperatures various lubricants and their application are of course known. For example, U.S. Pat. No. 2,841,244 discloses a mixture of vaporized, relatively volatile non-carbon forming hydrocarbon lubricating liquids and air as useful lubricants for aircraft gas turbine engines; operating temperatures of about 315.degree. C. are disclosed. U.S. Pat. No. 2,994,408 discloses another gaseous mixture for lubricating aircraft gas turbine engines subjected to temperatures of about 425.degree. C. U.S. Pat. No. 3,423,929 discloses a lubricating system for components of missiles, rockets and the like, which system includes a high temperature gas having solid graphite and sulfur particles entrained therein.
To date, however, neither the above nor other prior art lubricating systems have been found satisfactory for use with load bearing surfaces in engines operating at, or exposed to, temperatures in excess of about 475.degree. C., for extended periods or have proved not to be satisfactory for long term operation.